Add 'the easy way' basic instructions to README file
Create a MyMoip::Purchase class to provide an easy way to checkout

Unfinished but working class. Using Minitest/Spec style for tests.
Rename MyMoip::Purchase#credit_card_owner to #payer

Equal to MyMoip's class name.
Change gem's description
Update README and gemspec files due gem's new description
Remove jeweler dependency for gem generation
Merge remote-tracking branch 'origin/master' into purchase-class

Conflicts:
	README.md
Convert Purchase's tests to minitest's unit syntax
Rename required keys in README example of Purchase use
Merge branch 'remove_jeweler' into purchase-class

Conflicts:
	mymoip.gemspec
	test/helper.rb
Remove explicitly minitest requirement
Improve identation and (single) quotes use in README
Merge branch 'purchase-class'
Permit users to set purchases's reason initializing a MyMoip::Purchase
Raise exception when making an api call without token/key

Closes #23.
Merge branch 'master' into fix-commission-percentage-format

Conflicts:
	VERSION